Field of the Application
The application generally relates to management of call establishment information, and more particularly, to mobile communication devices, Mobility Management Entities (MMEs), Home Subscriber Server (HSS), and methods for providing assistance information for calls under Isolated E-UTRAN Operation for Public Safety (IOPS).
Description of the Related Art
To respond to the growing demand for ubiquitous computing and networking, various wireless technologies have been developed, including Global System for Mobile communications (GSM) technology, General Packet Radio Service (GPRS) technology, Enhanced Data rates for Global Evolution (EDGE) technology, Wideband Code Division Multiple Access (WCDMA) technology, Code Division Multiple Access 2000 (CDMA-2000) technology, Time Division-Synchronous Code Division Multiple Access (TD-SCDMA) technology, Worldwide Interoperability for Microwave Access (WiMAX) technology, Long Term Evolution (LTE) technology, LTE-Advanced (LTE-A) technology, and Time-Division LTE (TD-LTE) technology, etc.
Using release 13 of the LTE technology as an example, the concept of Isolated E-UTRAN Operation for Public Safety (IOPS) is proposed. Generally speaking, IOPS aims to maintain a certain level of services for public safety users even when the network is not fully functional, e.g., when an eNodeB or a set of eNodeBs has/have lost backhaul communications with the core network due to a large scale disaster. The standalone/nomadic eNodeB(s) may still create a serving radio access network without the backhaul communications, to provide service to users within the coverage of the eNodeB(s).
However, due to isolation from the core network, the standalone/nomadic eNodeB(s) cannot acquire necessary information for call establishment. As a result, the standalone/nomadic eNodeB(s) may not be able to process the user's call requests from its service region.